Method for ascertaining and visualizing network topologies

ABSTRACT

A method to ascertain a network topology, wherein a request message is transmitted from a first network node to at least one second network node connected to the first network node, a second network node enters its associated node number in the network into the request message and forwards the request message to at least one third network node connected to the second network node, the request message is forwarded until all the network nodes arranged in the network and all connecting lines connecting the network nodes have been passed through, the request message is transmitted back to the first network node, and the network topology information, available in the form of the node numbers entered in the request message, is stored.

BACKGROUND OF THE INVENTION

[0001] Communication networks and computer networks include networknodes, for example formed by communications installations and dataprocessing devices, as well as the connecting lines connecting theindividual network nodes to one another. In this context, a multiplicityof different network structures (also referred to in the literature asnetwork topologies) are known, such as a star network, a ring network, atree network, a chain network or a bus network.

[0002] In networks, a distinction is drawn between connectionless andconnection-oriented networks, according to the topology of therespective network. Connectionless networks omit a signaling phase whichprecedes information transmission between communication terminalsassociated with the networks and within the context of which aconnection is set up between the communication terminals. In aconnectionless network, for example, an IP-oriented (Internet Protocol)computer network, an information packet to be transmitted is transmittedto each communication terminal associated with the network. The decisionregarding which communication terminal processes the receivedinformation packet further or rejects it is made by the recipient of theinformation packet.

[0003] In a connection-oriented network, for example an ISDN-orientedcommunication network, in which information is transmitted from networknode to network node via a connection set up previously within thecontext of a signaling connection, an important feature for optimumtransmission of a message via the network is for the network topology tobe known; i.e., for information to be held about how the individualnetwork nodes are connected to one another.

[0004] The present invention is therefore directed toward providingmethods which permit network topologies to be ascertained andvisualized, particularly for a connection-oriented network.

SUMMARY OF THE INVENTION

[0005] Accordingly, in an embodiment of the present invention, a methodis provided for ascertaining network topologies, wherein: a request formessages is transmitted from a first network node to at least one secondnetwork node connected to the first network node; the second networknode enters its associated node number in the network into the requestmessage and forwards the request message to at least one third networknode connected to the second network node; the request message isforwarded until all the network nodes arranged in the network and allconnecting lines connecting the network nodes have been passed through;and the request message is transmitted back to the first network nodeand the network topology information, available in the form of nodenumbers entered in the request message, is stored.

[0006] In an embodiment, in cases in which the node number of the thirdnetwork node has already been entered in the request message, the thirdnetwork node enters its node number into the request message again andsends the request message back to the second network node.

[0007] In an embodiment, the second network node likewise enters itsnode number into the request message again and forwards the requestmessage to a further third network node.

[0008] In an embodiment, in cases in which the second network node hasno connecting lines to further third network nodes, the second networknode transmits the request message back to the first network node.

[0009] In an embodiment, the request message is transmitted via asignaling connection within the network.

[0010] In an embodiment, the information about the network topology isstored in tabular form, with two node numbers entered in succession inthe request message being respectively converted into an entry of thetable.

[0011] In an embodiment, the table is stored in a central dataprocessing device connected to the first network node.

[0012] In a further embodiment of the present invention, a method isprovided for visualizing the network topology, wherein: a networktopology in the form of a tree structure is developed from a table whichrepresents the network topology and includes information about networknodes and connecting lines of the network; the tree structure is used toascertain whether the network topology includes an annular network and,if this the case, the network topology is developed from that annularnetwork which includes the greatest number of network nodes; and, incases in which the network topology does not include an annular network,a network topology in the form of a chain-like network is developed.

[0013] In an embodiment, to develop the tree structure, starting from afirst network node as the root of the tree structure, second networknodes for which there is an entry available in the table's rowassociated with the first network node, are arranged in a nexthierarchical level of the tree structure, and then connections from thefirst network node to the second network nodes are inserted, andstarting from one of the second network nodes, third network nodes forwhich there is an entry available in the table's row associated with thesecond network node are arranged in a further next hierarchical level ofthe tree structure, ignoring those columns which are associated with thenetwork node which has already been taken into account, and thenconnections from the second network node to the first and third networknodes are inserted, and the method is then continued until all the rowsin the table have been processed.

[0014] In an embodiment, to ascertain whether the network topologyincludes an annular network, a bi-directional path which has the mostnetwork nodes within the tree structure is ascertained.

[0015] A fundamental advantage of this inventive method is that thenetwork topology of a network can be automatically ascertained from anydesired network node, and hence optimum transmission of messages (forexample within the context of “Least Cost Routing”) is made possible ina simple and convenient manner from this network node.

[0016] One advantage of refinements of the present invention is, amongother things, that transmitting a request message in order to ascertainthe network topology via a signaling connection, in particular aD-channel of an ISDN-oriented connection, within the network (frequentlyreferred to in the literature as “Temporary Signaling Connection”, TSCfor short) takes up only a small amount of transmission capacity withinthe network, and no charges for ascertaining the network topology ariseeither.

[0017] Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

[0018]FIG. 1 shows a structogram for schematically illustrating anexemplary network.

[0019]FIG. 2a shows a first flowchart to illustrate the fundamentalmethod steps of the present invention carried out for ascertaining thenetwork topology.

[0020]FIG. 2b shows a second flowchart to illustrate the fundamentalmethod steps of the present invention carried out for ascertaining thenetwork topology.

[0021]FIG. 3 shows a table which represents the network topology of thenetwork and includes information about network nodes and connectinglines in the network.

[0022]FIG. 4 shows a structogram to illustrate the network topology inthe form of a tree structure.

DETAILED DESCRIPTION OF THE INVENTION

[0023]FIG. 1 shows a structogram for an exemplary network KN, inparticular a connection-oriented network, which is used to illustratethe inventive method below. In this case, the network KN is anISDN-oriented communication network, for example. The network KNincludes a total of nine network nodes 1, . . . ,9, which areinterconnected with one another in the manner shown. In this case, thenetwork KN has a series of annular and chain-like network structures. Anetwork node can be produced, by way of example, by a communicationsinstallation or, alternatively, by an appropriately designed dataprocessing device; e.g., a personal computer or a workstation.

[0024] The network KN is connected to a local area network LAN via afirst network node 1. In this context, data are transmitted via thelocal area network LAN on the basis of the IP protocol (InternetProtocol). Connected to the local area network LAN is a “GRM server”(Global Routing Manager) which, in the present exemplary embodiment, isused for central administration of node numbers NODE-ID for the networknodes 1, . . . ,9 in the network KN. The node numbers NODE-ID can beused as a simple way for the individual network nodes 1, . . . ,9 toaddress one another. To be able to ensure unique addressing within thenetwork KN, it is necessary for the respective node numbers NODE-ID tobe unique.

[0025] Administration of the node numbers NODE-ID associated with thenetwork nodes 1, . . . ,9 in the network KN requires that the GRM serverreceive information about which network nodes 1, . . . ,9 within thenetwork KN are active; i.e., are registered on the network KN. Forcommunication with the GRM server, the first network node 1, therefore,has a communication unit (not shown), frequently referred to in theliterature as GRM client, which is used for transmitting the requiredinformation to the GRM server.

[0026]FIG. 2 (including both FIG. 2a and FIG. 2b) with FIG. 2b directlyfollowing FIG. 2a, shows a flowchart to illustrate the fundamentalmethod steps carried out within the context of the inventive method forascertaining the network nodes 1, . . . ,9 which are active orregistered on the network KN. In the present exemplary embodiment, onlythe first four network nodes 1, . . . ,4 in the network KN are shown. Inaddition, it is assumed that the network nodes 1,3, . . . ,9 in thenetwork KN have already been assigned a node number NODE-ID, with theexception of the second network node 2.

[0027] To ascertain the network topology from the GRM server, the GRMserver sends a request message via the local area network LAN to thefirst network node 1 or to the communication unit (not shown) of thefirst network node 1. The first network node 1 or the communication unit(not shown) of the first network node 1 converts the request messagefrom the IP protocol into the ISDN protocol, for example, and sends amessage “SETUP: Topology Request, NODE-ID: 1” to one of the networknodes 2, 4 connected to the first network node 1; in the presentexemplary embodiment, to the second network node 2. Since the secondnetwork node 2 in the network KN has not yet been assigned a node numberNODE-ID, it sends a message “NodeAssignmentRequest” to the first networknode 1. The first network node 1 then ascertains, by accessing the GRMserver, a free node number NODE-ID (in the present exemplary embodiment,the node number NODE-ID=2) and sends an appropriate response message“Ack/NodeAssignmentRequest NODE-ID:2” to the second network node 2. Thesecond network node 2, thus, has been assigned the node numberNODE-ID=2.

[0028] In a next step, the second network node 2 enters its node numberNODE-ID=2 into the request message and sends a message “SETUP: TopologyRequest, NODE-ID: 1,2” to one of the network nodes 3,4 connected to thesecond network node 2 (in the present exemplary embodiment, to the thirdnetwork node 3). This network node enters its node number NODE-ID=3 intothe request message and sends a message “SETUP: Topology Request,NODE-ID: 1,2,3” to one of the network nodes 4,5,8 connected to the thirdnetwork node 3 (in the present exemplary embodiment, to the fourthnetwork node 4). The fourth network node 4, in turn, enters its nodenumber NODE-ID=4 into the request message and sends a message “SETUP:Topology Request, NODE-ID: 1,2,3,4” to one of the network nodes 1,2connected to the fourth network node 4 (in the present exemplaryembodiment, to the first network node 1).

[0029] The first network node 1 recognizes that its node numberNODE-ID=1 has already been entered in the request message. The firstnetwork node 1 then enters its node number NODE-ID=1 into the requestmessage again and sends a message “RELEASE: Ack/Topology Request,NODE-ID: 1,2,3,4,1” back to the fourth network node 4. This network nodeenters its node number NODE-ID=4 into the request message again andsends a message “SETUP: Topology Request, NODE-ID: 1,2,3,4,1,4” to thenetwork node 2 not selected previously. The second network node 2likewise recognizes that its node number NODE-ID=2 has already beenentered in the request message and then enters its node number NODE-ID=2into the request message and sends a message “RELEASE: Ack/TopologyRequest, NODE-ID: 1,2,3,4,1,4,2” back to the fourth network node 4.

[0030] The fourth network node 4, thus, has no further connecting lines.It enters its node number NODE-ID=4 into the request message again andsends a message “RELEASE: Ack/Topology Request, NODE-ID:1,2,3,4,1,4,2,4” back to the third network node 3, from which itoriginally received the request message. Unlike the fourth network node4, the third network node 3 has further connecting lines, not yet takeninto account, to the network nodes 5 and 8 and continues the method withthe method steps described. In this context, the method is continueduntil all the information about the sub-network including the networknodes 3,5,6,7,8,9 is available at the third network node 3.

[0031] The third network node thus has no further connecting lines. Itthen enters its node number NODE-ID=3 into the request message again andsends a message “RELEASE: Ack/Topology Request, NODE-ID:1,2,3,4,1,4,2,4,3,5,6,7,8,3,8,7,5, 7,6,9,6,5,3” back to the secondnetwork node 2, from which it originally received the request message.The second network node, thus, likewise has no further connecting linesnot yet taken into account. It enters its node number NODE-ID=2 into therequest message and sends a message “RELEASE: Ack/Topology Request,NODE-ID: 1,2,3,4,1,4,2,4,3,5,6,7,8,3,8,7,5,7,6,9,6,5,3,2” back to thefirst network node 1, from which it originally received the requestmessage. The first network node, thus, likewise has no furtherconnecting lines not yet taken into account. It then enters its nodenumber NODE-ID=1 into the request message and, finally, sends a message“GRM server: Topology Result, NODE-ID: 1,2,3,4,1,4,2,4,3,5,6,7,8,3,8,7,5,7,6,9,6,5,3,2,1” to the GRM server. The GRM serverstores the network topology information, obtained via the requestmessage, in an appropriate manner in tabular form.

[0032] The messages for the request message are transmitted via asignaling connection, frequently referred to in the literature as“Temporary Signaling Connection” (TSC for short) in the network KN, forexample a D-channel of an ISDN connection. In this way, only a smallamount of transmission capacities are used within the network KN, and noadditional charges arise for ascertaining the network topology.

[0033]FIG. 3 now shows a table which represents the network topology ofthe network KN and includes information about the network nodes 1, . . .,9 and the connecting lines in the network KN. The table has arespective row and column for each network node 1, . . . ,9 in thenetwork KN, where a row contains the connecting lines leaving arespective network node 1, . . . ,9 and a column contains the connectinglines entering a respective network node 1, . . . ,9. By way of example,the first network node 1 is connected both to the second and to thefourth network node 2, 4 via a respective bidirectional connecting line.

[0034] The GRM server converts the information in the form of nodenumbers NODE-ID: 1,2,3,4,1,4,2,4,3,5,6,7,8,3,8,7,5,7,6,9,6,5,3,2,1,contained in the request message, into the described tabular form. Tothis end, the first node combination 1,2 is read from the requestmessage and a corresponding entry (1,2) is inserted in the first row andsecond column of the table. The next node combination 2,3, including thesecond node number NODE-ID=2 of the first node combination 1,2 and thenext node number NODE-ID=3 contained in the request message, is thenread from the request message and a corresponding entry (2,3) isinserted in the second row and third column of the table. This method iscontinued until all the node combinations contained in the requestmessage have been processed.

[0035]FIG. 4 now shows a structogram to show the network topology in theform of a tree structure. To develop the tree structure from the table,any desired network node 1, . . . ,9 in the network KN is selected asthe root EB0 of the tree structure. In the present exemplary embodiment,this is the first network node 1.

[0036] Starting from the first network node 1 as the root EB0 of thetree structure, those network nodes for which there is an entryavailable in the table's row associated with the first network node 1are arranged in a first hierarchical level EB1 of the tree structure. Inthe present exemplary embodiment, these are the second and fourthnetwork nodes 2,4. Next, the connections between the first network node1 and the second and fourth network nodes 2,4 are inserted on the basisof the entries in the row associated with the first network node 1. In anext step, starting from one of the network nodes 2,4 of the firsthierarchical level EB1 (in the present exemplary embodiment, from thesecond network node 2), those network nodes for which there is an entryavailable in the table's row associated with the second network node 2are arranged in a second hierarchical level EB2 of the tree structure,ignoring those columns which are associated with a network node 1 whichhas already been taken into account. In the present exemplaryembodiment, these are the third and fourth network nodes 3,4. Next, theconnections between the second network node 2 and the first, third andfourth network nodes 3, 4 are inserted on the basis of the entries inthe row associated with the second network node 2. The method describedis continued until all the rows and columns in the table have beenprocessed; i.e., in the present exemplary embodiment, up to a seventhhierarchical level EB7 of the tree structure.

[0037] To convert the network topology of the network KN from the treestructure into the real network structure, the tree structure issearched, starting from the root EB0, for ring structures; i.e., forbidirectional paths having the same starting and ending point. Thepresent tree structure contains a number of ring structures. By way ofexample, a bidirectional path 1,2,3,4,1 is obtained starting from theroot EB0 of the tree structure (illustrated by the dotted line in FIG.4). In addition, a bidirectional path 3,5,6,7,8,3 is obtained startingfrom the second hierarchical level EB2 (illustrated by the dot-dashedline in FIG. 4).

[0038] To show the network topology, the network topology is showngraphically starting with the largest ring structure 3,5,6,7,8,3; i.e.,with that bidirectional path which has the most network nodes. In asecond step, the second ring structure 1,2,3,4,1 having the common thirdnetwork node 3 is added. Finally, the connecting lines 2-4, 5-7 and 6-9which are still missing are added. The method described is a simple wayof obtaining the network topology shown in FIG. 1 for the network KN.

[0039] Although the present invention has been described with referenceto specific embodiments, those with skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the invention as set forth in the hereafter appended claims.

1. A method for ascertaining network topologies, the method comprisingthe steps of: transmitting a request message from a first network nodeto at least one second network node connected to the first network node;entering, via the second network node, an associated node number in thenetwork into the request message; forwarding, via the second networknode, the request message to at least one third network node connectedto the second network node; forwarding the request message until allnetwork nodes arranged in the network and all connecting linesconnecting the network nodes have been passed through; transmitting therequest message back to the first network node; and storing the networktopology information available in the form of the node number entered inthe request message.
 2. A method for ascertaining network topologies asclaimed in claim 1, the method further comprising the steps of:entering, via the third network node, an associated node number of thethird network node into the request message again in cases in which thenode number of the third network node already has been entered in therequest message; and sending, via the third network node, the requestmessage back to the second network node.
 3. A method for ascertainingnetwork topologies as claimed in claim 2, the method further comprisingthe steps of: entering, via the second network node, the node number ofthe second network node into the request message again; and forwarding,via the second network node, the request message to a further thirdnetwork node.
 4. A method for ascertaining network topologies as claimedin claim 3, the method further comprising the steps of: transmitting,via the second network node, the request message back to the firstnetwork node in cases in which the second network node has no connectinglines to further third network nodes.
 5. A method for ascertainingnetwork topologies as claimed in claim 1, wherein the request message istransmitted via a signaling connection within the network.
 6. A methodfor ascertaining network topologies as claimed in claim 1, wherein theinformation about the network topology is stored in tabular form, withtwo node numbers entered in succession in the request message beingrespectively converted into an entry of the table.
 7. A method forascertaining network topologies as claimed in claim 6, wherein the tableis stored in a central data processing device connected to the firstnetwork node.
 8. A method for visualizing a network topology, the methodcomprising the steps of: developing a network topology in the form of atree structure from a table which represents the network topology andcomprises information about network nodes and connecting lines of thenetwork; using the tree structure to ascertain whether the networktopology comprises an annular network; developing the network topologyfrom the annular network which comprises a greatest number of networknodes if the network topology comprises an annular network; anddeveloping a network topology in the form of a chain-like network if thenetwork topology does not comprise an annular network.
 9. A method forvisualizing a network topology as claimed in claim 8, wherein, todevelop the tree structure, starting from a first network node as a rootof the tree structure, second network nodes for which there is an entryavailable in the table's row associated with the first network node arearranged in a next hierarchical level of the tree structure, andconnections from the first network node to the second network node arethen inserted, wherein, starting from one of the second network nodes,third network nodes for which there is an entry available in the table'srow associated with the second network node are arranged in a furthernext hierarchical level of the tree structure, ignoring those columnswhich are associated with a network node which already has been takeninto account, and connections from the second network node to the firstand third network nodes are then inserted, and wherein the method iscontinued until all rows in the table have been processed.
 10. A methodfor visualizing a network topology as claimed in claim 8, wherein toascertain whether the network topology comprises an annular network, abi-directional path which has the most network nodes within the treestructure is ascertained.